The present invention relates to a synchronous motor and, more particularly, to a synchronous motor having shaded poles to provide a magnetic one-way directional system for the motor and proper positioning of its stator poles to provide good starting and running characteristics.
There is a multitude of applications for small synchronous motors of the type having a permanent magnet rotor. Many of these applications are in timing devices such as clocks and appliances using sequence switches such as automatic washers.
One of the problems associated with synchronous motors having permanent magnet rotors is that the rotors will run in either a clockwise or a counterclockwise direction when current is applied. Thus, the motor drive shaft could be driven in a direction counter to what is desired. The present motor solves this problem by use of shading means for the stator poles to provide a magnetic directional system.
The use of shading means, however, introduces a problem with the motor's running characteristics. More specifically, it is necessary for good, smooth running characteristics that the flux generated by the field coil be equalized between the shaded and unshaded stator poles. The present invention overcomes this problem by using varying pole widths.